1. Field of the Invention
This invention is in the field of protective caps for small caliber Armor-Penetrating Fin-Stabilized Discarding-Sabot (APFSDS) ammunition. The purpose of such caps is to protect the tapered front end of the fin stabilized penetrator from any damage during rough handling and to guide the front of the cartridge during feeding and chambering in an automatic cannon so that the trajectory of the penetrator does not deviate significantly from its predicted trajectory.
2. Description of the Prior Art
Conventional small-caliber APFSDS ammunition consists of a fin-stabilized, armor-piercing penetrator which is supported on the bore of an automatic cannon by means of a multiple segment sabot. Typically, the penetrator has a cylindrical body portion measuring approximately 8.3 mm in diameter, and a leading portion which tapers to a fine point for low aerodynamic drag. It is crucial that the point of the penetrator be well-protected, since mishandling can result in the point becoming dented, scratched or bent. Damage of this nature is clearly undesirable, since any irregularities in the streamlined surface of the penetrator will seriously impair the accuracy of the projectile or increase its aerodynamic drag, or both, and thus cause its trajectory to deviate significantly from its predicted trajectory which assumes that the leading, or tapered, portion of the penetrator will not be dented, scratched, or bent.
To prevent such damage from occurring, the ammunition assembly is normally provided with a one-piece protective cap which is fastened to the front end of the sabot. The cap protects the front end of the projectile during handling and provides a smooth surface at the forward end of the projectile so that the cartridge will readily feed and chamber in an automatic cannon. In addition, the cap is designed to separate from the sabot and the sabot from the projectile as the projectile exits the muzzle of the cannon in such a way that neither the cap nor the sabot interferes with the flight of the penetrator.
In the past, one-piece protective caps have been molded from polyethylene. Typically, the caps are molded with a reduced-diameter section enabling them to be snap-fit over a cooperating lip portion of the sabot. When a cartridge fitted with one of these caps is fired from an automatic cannon, a combination of air ram pressure and centrifugal force causes the cap to split and detach from the sabot, hopefully without interfering with the trajectory of the penetrator.
It has been found, however, that the conventional polyethylene caps do not function as effectively as desired. They have been known to separate prematurely from the sabot during rough handling, leaving the penetrator unprotected. At other times, they have failed to separate properly, or have fragmented in such a way as to disturb the trajectory of the penetrator. If these events happen, the accuracy and effectiveness of the ammunition is significantly impaired.
Therefore, a need exists for a new and improved protective cap for small caliber APFSDS ammunition, which provides better protection of the penetrator during handling, and which breaks apart "cleanly" at muzzle exit, to avoid causing the penetrator to deviate from its desired trajectory or to reduce the penetrators terminal velocity, and thus its ability to penetrate a target.